We’ve all experienced this; you get ready for bed, and you turn the lights off, but you just can’t seem to doze off. You open your eyes and you can’t see anything. It takes a couple of minutes for your eyes to adjust to the dark. This is called ”dark adaptation”.
In order for night vision and dark adaptation to be successful, many physiological, neurological and biochemical mechanisms must take place behind the scenes. But how does this work? Your eye has, in addition to other cells, rod cells and cone cells, which are found on the retina at the back of the eye. Together they form the sensory layer that enables the eye to pick up light and color. Cones and rods are spread throughout the entire retina, except for in the small area opposite the pupil known as the fovea. The fovea has only cone cells, and its main function involves creating a focused image. You may have heard that the cones contribute to color vision, and the rods are sensitive to light.
Considering these facts, if you’re attempting to make out an object in the dark, like the edge of the last stair in a dark basement, instead of looking right at it, try to use your peripheral vision. If, on the other hand, you focus on the object itself, you’ll use the fovea, which is made up of cone cells that are less responsive in low light conditions.
The pupils also dilate when it’s dark. It takes fewer than sixty seconds for the pupil to completely enlarge but your eyes will get better at seeing in the dark over a half hour time frame.
Dark adaptation occurs when you walk into a darkened theatre from a bright area and have a hard time finding somewhere to sit. But soon enough, you adapt to the situation and see better. This same thing occurs when you’re looking at the stars in the sky. At first you won’t see many. Keep looking; while you dark adapt, the stars will become easier to see. While it takes several moments to get used to the dark, you’ll always be able to re-adapt to exposure to bright light, but if you return to the darker setting, your eyes will need time to re-adjust again.
This explains why many people prefer not to drive at night. When you look at the ”brights” of a car heading toward you, you may find yourself momentarily blinded, until that car is gone and your eyes readjust to the night light. To prevent this, don’t look directly at headlights, and learn to use your peripheral vision in those situations.
If you’re finding it challenging to see at night or in the dark, schedule a consultation with our doctors who will confirm that your prescription is up to date, and rule out other reasons for decreased vision, such as macular degeneration or cataracts.